In a known apparatus for mass transfer between a liquid and a gas inside a rotor having a packing, the liquid is introduced at the center of the rotor and driven outward through the packing by the centrifugal force generated by rotation of the rotor, and the gas surrounding the rotor is forced inward through the rotor by the gas pressure, counter to the liquid flow in the rotor.
WO 2015/101826 (U.S. Pat. No. 9,987,589) and WO 2016/038480 (US 2017/0028311) disclose mass-transfer machines having a rotor that has two spaced disks, a packing that drives centrally delivered liquid outward as the rotor rotates in the space between the two faces. Here the rotor is surrounded by a gas that due to the gas pressure flows through the rotor counter to the liquid, in order to produce a mass transfer between the liquid and the gas.